The present invention is directed to novel compounds, to a process for their preparation, their use and pharmaceutical compositions comprising said novel compounds. These novel compounds are useful in therapy, particularly for the treatment of type 2 diabetes.
Phosphorylation on serine, threonine and tyrosine amino acid residues in downstream proteins forms the major output from growth factor and cytokine receptors, from which a cellular response is built. A large number of growth factor and cytokine-regulated protein tyrosine kinases (PTKs) have been identified which can be integral parts of receptor proteins or cytosolic molecules (Al-Obeidi, FA, Wu, JJ and Lam, KS, Biopolym. Pept. Sci. Sect. 47, 197-223). These serve to phosphorylate proteins on tyrosine residues within specific primary amino acid sequences which, when phosphorylated, act as docking points for proteins that contain SH2 domains. It is the docking of proteins to phosphorylated tyrosine residues that contributes to the activation of such proteins and the establishment of a signal transduction cascade.
The overall output from signal transduction cascades is derived from the balance between phosphorylation and dephosphorylation of proteins. Phosphotyrosines are returned to their free acid form by the action of protein tyrosine phosphatases (PTPs) (Zhang, Z Y (1998) Crit. Rev. Biochem. Mol. Biol., 33, 1-52). Whilst a large number of PTKs has been identified (Hunter, T (1994) Sem. Cell Biol. 5, 367-376), the number of PTPs identified to date is decidedly smaller (van Huijsduijnen, R H (1998) Gene 225, 1-8). Despite the smaller number of enzymes in the PTP family available for investigation, a detailed understanding of the roles they play in signal transduction and disease has not been forthcoming. This is due in part to the lack of small molecule inhibitor molecules which are specific for members of the PTP family and which are permeable to the cell membrane and can thus be used in cell-based experiments. Furthermore, whilst experiments in transgenic animals can be and have been performed in which individual PTPs can be ablated, the effects of the loss of function of a specific enzyme may be masked by compensation by other members of the PTP family. Thus, the availability of small molecule inhibitors of PTPs would be very useful to the study of this important family of enzymes.
A role for the PTP family of proteins in ontogeny and disease is now becoming clearer (Li, L and Dixon, J E (2000) Sem. Immunol. 12, 75-84). Thus, experiments with gene knockouts in transgenic animals has revealed that the motheaten phenotype of mice in which cells of the haematopoietic lineage undergo hyper-proliferation is due to the loss of normal SHPTP1 function (Schultz, L D, Schweitzer, P A, Rajan, T V, Yi, T and Ihle, J N (1993) Cell 73, 1445-1454). Loss of function in the receptor-like subfamily of PTPs leads to conditions such as heightened and reduced sensitivity to insulin (Ren, J-M, Li, P-M, Zhang, W-R, Sweet, L J, Cline, G, Shulman, G I, Livingston, J N and Goldstein, B J (1998) Diabetes 47, 493-497), stunted growth and neurological disruption (Elchelby, M, Wagner, J, Kennedy, T E, Lanctot, C, Michaliszyn, E, Itie, A, Drouin, J and Tremblay, M L (1999) Nature Genet. 21, 330-333) and blockages in T cell maturation (Kishihara, K, Penninger, J, Wallaca, V A, Kundig, T M, Kawai, K, Wakeham, A, Timms, E, Pfeffer K, Ohashi, P S and Thomas P L (1993) Cell 74, 143-156).
The recent descriptions of mice in which the PTP PTP1B had been disrupted revealed that loss of function of this enzyme leads to enhanced insulin sensitivity and resistance to the development of obesity, thus revealing a therapeutic need for the development of specific PTP inhibitors (Elchelby, M, Payette, P, Michaliszyn, E, Cromlish, W, Collins, S, Loy, A L, Normandin, D, Cheng, A, Himms.Hagen, J, Chan, C C, Ramachandran, C, Gresser, M J, Tremblay, M L and Kennedy, B P (1999) Science 283, 1544-1548; Klaman, L D, Boss, O, Peroni, O D, Kim, J K, Martino, J L, Zablotny, J M, Moghal, N, Lubkin, M, Kim, Y-B, Sharpe, A H, Stricker-Krongrad, A, Shulman, G I, Neel, B G and Kahn, B B (2000) Mol. Cell. Biol. 20, 5479-5489). The mechanism of insulin action depends critically upon the phosphorylation of tyrosine residues in several proteins in the insulin signaling cascade. PTPs that dephosphorylate these proteins are important negative regulators of insulin action. Therefore, the use of specific PTP inhibitors may therapeutically enhance insulin action.
The anabolic effects of insulin are triggered through the activation of a variety of signal transduction cascades which lie downstream of the insulin receptor (Gustafson, T. A., Moodie, S A and Lavan, B E (1999) Rev. Physiol. Biochem. Pharmacol. 137, 71-190). The varieties of signals that are activated by insulin are thought to contribute to the range of effects that insulin controls. However, each pathway is activated by a common series of biochemical reactions proximal to the insulin receptor. Thus, the insulin receptor undergoes autophosphorylation on tyrosine residues when activated by insulin, and also phosphorylates other proteins, in particular, the insulin receptor substrate proteins (IRSs). It has now become widely accepted that the resistance to insulin that is a feature of type 2 diabetes results in part from dysfunctions in signal transduction activated by the insulin receptor, in particular in steps early in the signaling cascades which are common to different pathways (Virkamxc3xa4ki, A, Ueki, K and Kahn, R C (1999) J. Clin. Invest 103, 931-943; Kellerer, M, Lammers, R and Hxc3xa4ring, H-U (1999) Exp. Clin. Endocrinol. Diabetes 107, 97-106).
The signals that emanate from the insulin receptor are switched off by the returning of the insulin receptor and other components of the signal transduction cascades to their basal, non-active states. For the insulin receptor and the IRS proteins, this is achieved by dephosphorylation of phosphotyrosine residues. It is now becoming clear that different PTPs may regulate the insulin receptor in different tissues, but the number of candidate enzymes which do this is small (Wxc3xa4lchi, S., Curchod, M-L., Pescini Gobert, R., Arkinstall, S. and Hooft van Huijsduijnen, R. (2000) J. Biol. Chem. 275, 9792-9796). Thus, protein tyrosine phosphatase 1B (PTP1B) appears to be the major negative regulator of the insulin receptor in muscle and liver tissues (see for example Elechelby, M, Payette, P, Michalszyn, E, Cromlish, W, Collins, S, Loy, A L, Normandin, D, Cheng, A, Himms-Hagen, J, Chan, Cxe2x80x94C, Ramachandran, C, Gresser, M J, Tremblay, M and Kennedy, B P (1999) Science, 283, 1544-1548; Goldstein, B J, Bittner-Kowalczyk, A, White, M F and Harbeck, M (2000) J. Biol. Chem. 275, 4283-4289). By contrast, PTP alpha may play a more dominant role in regulating the insulin receptor in adipose tissue (Calera, M R, Vallega, G and Pilch, P F (2000) J. Biol. Chem. 275 6308-6312).
The development of type 2 diabetes is characterised by a protracted period of insulin resistance. In human subjects who are obese and insulin resistant, PTP protein concentrations are increased, which has led to the idea that elevations in the proteins contributes to the cause of the diabetic state (Ahmad, F, Azevedo, J L, Cortright, R, Dohm, G L and Goldstein, B J (1997) J. Clin. Invest. 100 449-458). The two most significantly elevated are PTP1B and LAR. Considering that loss of LAR activity is associated with insulin resistance and diabetes (Ren, J-M, Li, P-M, Zhang, W-R, Sweet, L J, Cline, G, Shulman, G I, Livingston, J N and Goldstein, B J (1998) Diabetes 47 493-497), these data support the concept that PTP1B is a major contributor to the insulin resistant state and that pharmacological inhibition of its activity may go some way towards pharmaceutically alleviating the condition. Indeed, the recent reports of the knockout mouse in which PTP1B has been ablated confirm that loss of PTP1B activity leads to enhancement of the metabolic effects of insulin (Elechelby, M, Payette, P, Michalszyn, E, Cromlish, W, Collins, S, Loy, AL, Normandin, D, Cheng, A, Himms-Hagen, J, Chan, C-C, Ramachandran, C, Gresser, M J, Tremblay, M and Kennedy, B P (1999) Science, 283, 1544-1548; Klaman, L D, Ross, O, Peroni, O D, Kim, J K, Martino, J L, Zabolotny, J M, Moghal, N, Lubkin, M, Kim, Y-B, Sharpe, A H, Stricker-Krongrad, A, Shulman, G I, Neel, B G and Kahn, B B (2000) Mol. Cell. Biol. 20 5479-5489). Furthermore, inhibition of PTP1B with a specific small molecule has been reported to treat the symptoms of diabetes in the ob/ob mouse (Wrobel, J, Sredy, J, Moxham, C, Dietrich, A, Li, Z, Sawicki, D R, Seestaller, L, Wu. L, Katz, A, Sullivan, D, Tio, C and Zhang, Z-Y (1999) J. Med. Chem. 42 3199-3202).
The patent application with the publication no. WO 96/40113, discloses heterocyclic nitrogen containing compounds, such as nitropyridine or nitrothiazole, capable of inhibiting protein tyrosine phosphatase activity. Such molecules are disclosed as being useful to modulate or regulate signal transduction by inhibiting protein tyrosine phosphatase activity and to treat various disease states including diabetes mellitus.
WO 98/27065 discloses a class of compounds which are stated as being protein tyrosine phosphatase modulating compounds. These prior art compounds are however structurally distinct from the compounds claimed in the present patent application.
WO 97/08934 discloses aryl acrylic acid compounds of a certain structure, which compounds are stated as having protein tyrosine protease modulating activity. Also these prior art compounds are however structurally distinct from the compounds claimed in the present patent application.
WO 99/58519 discloses certain phenyl oxo-acetic acid compounds. These compounds are stated as being useful in the treatment of metabolic disorders related to insulin resistance and hyperglycemia. Also these prior art compounds are however structurally distinct from the compounds claimed in the present patent application.
WO 99/58521 discloses the use of 11-aryl-benzo[b]naphtho[2,3-d]furan and 11-aryl-benzo[b]naphtho[2,3-d]thiophene compounds to inhibit protein tyrosine phosphatase activity. Such compounds are disclosed as being useful to modulate or regulate signal transduction by inhibiting protein tyrosine phosphatase activity and to treat various disease states including diabetes mellitus.
The preparation of the compound 4-hydroxy-3,3-dimethyl-2H-benzo[g]indole-2,5(3H)-dione, said compound having the chemical structure 
is disclosed by Siegfried Petersen et al. in Justus Liebigs Ann. Chem. (1972), 764, pp. 50-57. However, this prior art document does not disclose or even suggest that this compound may have therapeutic activity, and particularly not in the diabetes area, such as type 2 diabetes.
The object of the present invention was to provide novel compounds having improved advantages over drugs currently used for the treatment of type 2 diabetes. It should be appreciated that the wording xe2x80x9cimproved advantagesxe2x80x9d is not necessarily defined as more potent compounds, but as compounds having improved advantages overall, including but not limited to also improved selectivity and less side-effects.
The novel compounds according to the present invention are defined by the general formula I 
wherein
R1 is
(i) hydrogen;
(ii) linear or branched C1-C6 alkoxy;
(ii) xe2x80x94Oxe2x80x94(C1-C6 alkyl)xe2x80x94Q, where the alkyl group may be linear or branched, and where Q is phenyl, naphthyl, or a heterocycle having from 5 and up to 10 ring atoms, where at least one of the ring atoms is an atom other than carbon, such as O, N, or S (e.g., R1 can be xe2x80x94O-methyl-phenyl, xe2x80x94O-ethyl-phenyl, or xe2x80x94O-propyl-phenyl); and 
where n is an integer 1 or 2; and each of Q1 and Q2 is independently hydrogen or C1-C6 alkyl where the alkyl group may be linear or branched (e.g., methyl or ethyl); or 
where n is an integer 1 or 2;
R2 is
(i) hydroxy;
(ii) linear or branched C1-C6 alkoxy (e.g., C1-C3 alkoxy);
(iii) xe2x80x94Oxe2x80x94COxe2x80x94(C1-C6 alkyl) where the alkyl group may be linear or branched (e.g., xe2x80x94Oxe2x80x94CO-methyl or xe2x80x94Oxe2x80x94CO-methyl); or
(iv) xe2x80x94Oxe2x80x94CO-phenyl, or xe2x80x94Oxe2x80x94CO-naphthyl;
each of R3 and R4 is independently
(i) C1-C6 alkyl, where the alkyl group may be linear or branched (e.g., methyl or ethyl); or
(ii) cyclopentane, or cyclohexane;
the compound 4-hydroxy-3,3-dimethyl-2H-benzo[g]indole-2,5(3H)-dione being excluded.
The invention also features compounds of formula Ia 
wherein each of R1, R2, R3 and R4 has been defined in formula I above, and wherein Ra is xe2x80x94CH2xe2x80x94COxe2x80x94(C1-C6 alkyl) where the alkyl group may be linear or branched (e.g., xe2x80x94CH2xe2x80x94CO-methyl or xe2x80x94CH2xe2x80x94CO-ethyl);
The invention further features compounds of formula Ib 
wherein each of R1, R2, R3 and R4 has been defined in formula I above, and wherein Rb is
(i) xe2x80x94COxe2x80x94(C1-C6 alkyl) where the alkyl group may be linear or branched (e.g., xe2x80x94CO-methyl or xe2x80x94CO-ethyl); or
(ii) hydrogen.
Within the scope of the invention are also pharmaceutically and pharmacologically acceptable salts of a compound of formula I, formula Ia, and formula Ib, as well as hydrates thereof.
Some specific examples of R1 in accordance with the present invention are hydrogen, methoxy, ethoxy, propoxy, butoxy, pentoxy, and hexyloxy, wherein said alkoxy substituents may be linear or branched. Another specific example of R1 in accordance with the present invention is phenyl-(CH2)nxe2x80x94Oxe2x80x94 where n is an integer 1, or 2. Still another specific example of R1 in accordance with the invention is H2Nxe2x80x94COxe2x80x94CH2xe2x80x94Oxe2x80x94.
Some specific examples of R2 in accordance with the present invention are hydroxy; methoxy, ethoxy, propoxy, butoxy, pentoxy, and hexyloxy, wherein said alkoxy substituents may be linear or branched; xe2x80x94Oxe2x80x94COxe2x80x94(CH2)nxe2x80x94CH3 wherein n is an integer 0, 1, 2, 3, 4 or 5 (e.g., xe2x80x94Oxe2x80x94COxe2x80x94CH2xe2x80x94CH3); xe2x80x94Oxe2x80x94CO-phenyl; and xe2x80x94Oxe2x80x94CO-naphthyl.
Some specific examples of R3 and R4 in accordance with the present invention are methyl, ethyl, propyl, butyl, pentyl, and hexyl, wherein the alkyl groups may be linear or branched; cyclopentyl; and cyclohexyl.
A specific example of Ra in accordance with the present invention is xe2x80x94CH2xe2x80x94COxe2x80x94(CH2)nxe2x80x94CH3 wherein n is an integer 0, 1, 2, 3, 4 or 5 (e.g., xe2x80x94CH2xe2x80x94COxe2x80x94CH2xe2x80x94CH3, xe2x80x94CH2xe2x80x94COxe2x80x94(CH2)2xe2x80x94CH3, or xe2x80x94CH2xe2x80x94COxe2x80x94(CH2)3xe2x80x94CH3).
A specific example of Rb in accordance with the present invention is xe2x80x94COxe2x80x94(CH2)nxe2x80x94CH3 wherein n is an integer 0, 1, 2, 3, 4 or 5 (e.g., xe2x80x94COxe2x80x94CH3, xe2x80x94COxe2x80x94CH2xe2x80x94CH3, or xe2x80x94COxe2x80x94(CH2)2xe2x80x94CH3).
A subset of the compounds of the invention include compounds of formula I, formula Ia, or formula Ib wherein R1 is linear or branched C1-C6 alkoxy, phenyl-(CH2)nxe2x80x94Oxe2x80x94 where n is an integer 1 or 2, or H2Nxe2x80x94COxe2x80x94CH2xe2x80x94Oxe2x80x94; and R2 is linear or branched C1-C6 alkoxy, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)nxe2x80x94CH3 where n is an integer 0, 1, 2, 3, 4 or 5, xe2x80x94Oxe2x80x94CO-phenyl, or xe2x80x94Oxe2x80x94CO-naphthyl. Another subset of compounds of the invention include compounds of formula I, formula Ia, or formula Ib wherein R1 is hydrogen, linear or branched C1-C6 alkoxy, phenyl-(CH2)nxe2x80x94Oxe2x80x94 where n is an integer 1 or 2, or H2Nxe2x80x94COxe2x80x94CH2xe2x80x94Oxe2x80x94; R2 is hydroxy, linear or branched C1-C3 alkoxy, or xe2x80x94Oxe2x80x94COxe2x80x94(CH2)nxe2x80x94CH3 where n is an integer 0, 1, 2, or 3; and R3 and R4 are each and independently linear or branched C1-C3 alkyl. Still another subset of the invention include compounds of formula I, formula Ia, or formula Ib wherein R1 is hydrogen, linear or branched ethoxy, propoxy, or butoxy; phenyl-(CH2)nxe2x80x94Oxe2x80x94 where n is an integer 1 or 2; or H2Nxe2x80x94COxe2x80x94CH2xe2x80x94Oxe2x80x94; R2 is hydroxy; methoxy, xe2x80x94Oxe2x80x94COxe2x80x94CH3; R3 and R4 are each methyl; Ra is xe2x80x94CH2xe2x80x94COxe2x80x94CH3; and Rb is xe2x80x94COxe2x80x94CH3.
The compounds according to the present invention are useful in therapy, particularly for the treatment of type 2 diabetes mellitus.
Also within the scope of the invention is the use of a compound of the formula I, for the manufacture of a medicament for the treatment of type 2 diabetes mellitus.
A further aspect of the invention is the use of a compound of the formula Ia, for the manufacture of a medicament for the treatment of type 2 diabetes mellitus.
Still a further aspect of the invention is the use of a compound of the formula Ib, for the manufacture of a medicament for the treatment of type 2 diabetes mellitus.
A further aspect of the invention is a method for the treatment of a patient suffering from type 2 diabetes mellitus, whereby an effective amount of a compound according to formula I above, is administered to a patient in need of such treatment.
A further aspect of the invention is a method for the treatment of a patient suffering from type 2 diabetes mellitus, whereby an effective amount of a compound according to formula Ia above, is administered to a patient in need of such treatment.
Still a further aspect of the invention is a method for the treatment of a patient suffering from type 2 diabetes mellitus, whereby an effective amount of a compound according to formula Ib above, is administered to a patient in need of such treatment.
As used herein, an alkyl is a straight or branched hydrocarbon chain containing the indicated number of carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-methylpentyl, and n-hexyl.
By cycloalkyl is meant a cyclic alkyl group containing the indicated number of carbon atoms. Some examples of cycloalkyl are cyclopropyl, cyclopentyl, cyclohexyl, adamantyl, and norbornyl. Heterocycloalkyl is a cycloalkyl group containing the indicated number of heteroatoms such as nitrogen, oxygen, or sulfur. Examples of heterocycloalkyl include piperidinyl, piperazinyl, tetrahydropyranyl, tetrahydrofuryl, and morpholinyl.
As used herein, aryl is an aromatic group containing the indicated number of ring atoms. Examples of an aryl group include phenyl, naphthyl, phenanthryl, and anthracyl. Heteroaryl is aryl containing the indicated number of heteroatoms such as nitrogen, oxygen, or sulfur. Some examples of heteroaryl are pyridyl, furanyl, pyrrolyl, thienyl, thiazolyl, oxazolyl, and imidazolyl.
Each of the cycloalkyl, heterocycloalkyl, aryl, or heteroaryl groups described herein is optionally substituted with C1-4 alkyl, C3-6 cycloalkyl, 3-6 membered heterocycloalkyl, C6-10 aryl, 6-10 membered heteroaryl, C7-14 aralkyl, C1-4 alkyl-heteroaryl with 6-10 ring atoms, C1-4 alkoxy, hydroxy, hydroxyl-C1-4 alkyl, carboxyl, halo, halo-C1-4 alkyl, amino, amino-C1-4 alkyl, nitro, cyano, C1-5 alkylcarbonyloxy, C1-5 alkyloxycarbonyl, C1-5 alkylcarbonyl, formyl, oxo, aminocarbonyl, C1-5 alkylcarbonylamino, C1-4 alkylsulfonylamino, aminosulfonyl, aminocarbonyloxy, or C1-4 alkyloxycarbonylamino.
Note that an amino group can be unsubstituted, mono-substituted, or di-substituted. It can be substituted with groups such as C1-4 alkyl, C3-6 cycloalkyl, 3-6 membered heterocycloalkyl, C6-10 aryl, or 6-10 membered heteroaryl. Halo refers to fluoro, chloro, bromo, or iodo.
The compounds according to the present invention may be prepared as described by the following methods.
The compounds of formula I can be synthesized from the corresponding 5 and 6-hydroxyquinone according to the procedure reported by Ley and Nast Angew. Chem. 1967, 79, 150 (see Schemes 1 and 2 below). The starting material 5-hydroxyquinone is commercially available from Aldrich. Another starting material silver oxide can be prepared according to a literature procedure (Vogel""s textbook of practical Organic Chemistry 5Th Edition, p677) and stored under inert atmosphere in the dark until used. Freshly prepared silver oxide generally gives the best results. 
The invention will now be described in more details in the following Examples, which however should not be construed as limiting the invention. In the following examples, column chromatography was carried out using either normal glass columns and compressed air or pumps and fractions collectors. The packing materials used were Merck Silica Gel 60 (230-400 mesh) or YMC-GFL Silica 60 xc3x85 S-50 Mesh. 1H NMR and 13C NMR were recorded on a Varian at 500 MHz and at 125.7 MHz, respectively. 1H NMR and 13C NMR spectra were referenced to residual solvent or to tetramethylsilane as internal standard. EI MS spectra were obtained on Micromass Quattro I instrument. Elementary analyses were performed at a Vario EL instrument (Elementar Analysensysteme GmbH, Hanau, Germany).